Variable speed unit



Dec. 26, 1933. P. B. REEVES I 1,941,417

.VARIABLE SPEED UNIT Filed April 23, 1930 s Sheets-Sheet 1 15 Angie 120pm tioned to relation of Driving and Driven Shafts IN VEN TOR.

Fall; 15. fieewcfl ATTORNEYS 3 Sheets-Sheet 2 DDDDJ'IE 5a 5 P. B. REEVESVARIABLE SPEED UNIT Filed April 23, 1930 DDDDDDDDDDDDDDD INVENTOR;Pau1D.Ree1 e 5,

ATTORNEYS Dec. 26, 1933 P. a. REEvEs VARIABLE sPEEb UNIT Filed A ril 23.1930 3'Sheets-Sheet s 1 N VEN TOR.

5 W M e W H ut [TA B M I.

Patented Dec. 26, 1933 UNITED s'rA VARIABLE SPEED UNIT Paul B. Reeves,Indianapolis, lnd., assignor to Reeves Pulley Company, Columbus, Ind., acorporation of Indiana Application April 23, 1930. Serial No. 446,675

scam.

The object of my invention is to produce a speed-varying transmissionunit of simple char acter embodying a V-belt, a cooperating pair ofoppositely placed cones which are spring-pressed together and betweenwhich the-belt rides at various radii with its edges in engagement withthe cones, a cooperating fixed diameter grooved pulley over which thebelt also rides, and means for simultaneously shifting either the fixeddiameter pulley or the cone-pair both laterally and axially, whereby thebelt may be caused to cooperatively engage the cone-pair at any desired.radius under such conditions that the belt in any position ofadjustment will not have any tendency 16 to ride the flanges of thefixed-diameter pulley.

The accompanying drawings illustrate my invention.

Fig. 1 is a plan of a unit embodying my invention with a portion of thebelt broken away to show the cone-pair carried by the motor shaft;

Fig. 2 is an end elevation in partial vertical sec- .tion of theconstruction shown in Fig. 1, wherein 'the motor shaft isadjustable inthe plane of, the

driven shaft;

Fig. 3 is a view similar to Fig. 2 but with the .motor shaft arrangedfor adjustment in a plane other than the plane of the driven shaft;

Fig. 4 is a diagram showing the manner of determining the guide anglealong which the motor shaft must be laterally adjustable to produce theaxial displacement necessary to keep the belt in a plane at right anglesto the axes of the driving and driven shafts! Fig. 5 i a transversesection of a V-belt of the Reeves-transmission type which is moreefficient, in larger powers, than the solid leather belt indicated inthe other figures.

In the drawings 10 indicates a fixed-diameter grooved pulley carried byshaft '11 of any mechanism 12 which is to be driven at variable speeds.

The driving motor 13, most conveniently a small electric motor, hassecured to its shaft 14 an axially fixed cone 15 having a sleeve-hubupon which is splined an opposed cone 15 urged toward cone 15 by aspring 16 which may be placed under any desired degree of compression bynut 17 mounted on the sleeve of cone l5.

Passing over the pulley l0 and between the cones 15, 15, with its edgesin frictional contact with the cone faces, is an endless V-belt 20. Thebelt 20, for small power machines, may be conveniently an ordinary thickleather belt with its edges chamfered to a proper angle to efiicientlyfrictiohally coact with the cone surfaces, and for 55 larger powertran'smissionthe belt 20 may be of the. well-known Reeves transmissiontype comprising a central endless web 25 and transverse stiffeningblocks 26, 26 the ends. of which carry suitable friction faces 27.

The belt 20, being of fixed length, may be caused to engage the conepair at different radii by varying the distance between the centers ofthe two shafts l1 and 14, spring 16 serving to keep the cones in properengagement with the edges of the belt, but variation of the distancesbetweenthe shaft centers causes a variation in the distance between thetwo cones so that the transverse plane medially between the cones willshift. axially of the driving shaft.

'Proper operation of a V-belt requires that the median planes of the twocoacting grooved pulleys must at all times be coincident andconsequently in order that these two median planes may at all times becoincident it is necessary to axially shift one shaft or the otherconcurrently with the lateralshifting of one shaft or the other. Mostconveniently the concurrent axial and lateral changing of relationshipbetween the shafts is accomplished by proper movement of one shaft andthis movable shaft is preferably the shaft 14 which carries the conepair which, in turn, is

most conveniently the shaft of the driving motor.

The amount of variation of distance between the shaft centers in orderto get the desired range of speed variation will be first dependent uponthe desired difference between maximum and minimum operating radii ofthe cones, i. e., the radii of the desired maximum and minimum contactsbetween the belt and the cones; second, upon the pitch of the cones, i.e., one-half the conical angle; and third, upon the relation which theplane of movement of the' shii'table shaft bears to a parallel planepassing through the fixed shaft, i. e., upon whether or not the plane ofmovement of the movable shaft passes through the axis of the fixed shaftor is tangent thereto at a greater or lesser radius.

In practice, for many years, speed-varying friction cones have beenfound to be most efficient if the conical angle is 144 degrees, 1. e.,the cone face is pitched 18 degrees fromthe transverse medial planebetween the cones.

In order to simultaneously vary the distance between the centers ofshafts 11 and 14, to obtain desired speed variation, and at the sametime shift the'cone l5 axially so that the medial transverse planebetween the cones will at all times be par supported in guideways 31which lie at an appropriate angle to the axes of the two shafts 11 and14.

It has heretofore been supposed (see for instance U. S. Patent 998;733,issued July 25, 1911 to Alfred Aichele) that the necessary angle ofsliding movement should be the angle of the cone faces, but when such anarrangement is produced it has been found that, except in one positionof speed adjustment, the belt has such a tendency to ride the flanges ofthe fixed-diameter pulley that the belt soon becomes so edge-worn as tomake the apparatus commercially impracticable.

I have discovered the fundamental error which resides in the disclosureof the above-mentioned patent, said fundamentalerror being, that theangle of lateralmovement of the cone pair, in-

stead of being equal to the cone'angle, must be a very much smallerangle, the exact angularity of which is dependent primarily (assumingany given cone angle), upon the relation which the plane of lateralmovement of the motor shaft bears to the plane of the fixed shaft.

I illustrate in the diagram of Fig. 4 a graphic method of determiningthe necessary adjustment angle. y

In this diagram I indicate the cone pair in five successive positions,A, B,'C, D and E, position A assuming a lateral adjustment in the planeAP passing through the axis of shaft 11; position B having an adjustmentplane BP displaced from plane AP a distance equal to the sine of anangle of twenty-two and one-half degrees multiplied by the minimumdistance between the shaft centers, (i. e., the belt 20 at that timehaving its largest radius of contact with the cone pair) and positionsC, D and E indicating adjustment planes -CP, DP and EP displaced fromplane AP fortyfive degrees, sixty-seven and one-half degrees and ninetydegrees respectively.

The are X, having a radius equal to the minimum distance between theshaft centers, will pass through the centers of shaft 14 at its variouspositions A, B, C, D and E. Assuming that, in position A, shaft 14 mustbe moved to position AM where it. is at its maximum distance from -shaft11, tothus cause minimum radius of contact between belt 20 and the conepair, an arc Y drawn through the center of shaft 14 at position AM andwith the center at the axis of shaft 11, will be the locus of maximumposition centers of shaft 14. The distance 40 between the centers ofshaft 14 in positions A and AM, in the plane AP, will thus be the amountof lateral shift which will be necessary to produce the desired contactradius variation between the belt 20 and the cone pair, when the shaft14 is laterally shifted in plane AP.v Correspondingly, the distances 41,42, 43 and 44 will be the corresponding necessary lateral movements ofshaft 14 when the lateral adjustment .occurs respectively in planes 3?,DP and EP. Referring now to the lower part of diagram 4, it will benoted that the fixed diameter pulley 10 and the cone pair 15 and 15' andshafts 11 and 14 in minimum and maxi.- mum positions 14A and 14AM, areshown in plan.

In order that there may be' no tendency of the belt 20 to ride oneflange or the other of the grooved pulley 10, it must be assumed thatthe edge Z of belt 20 will remain in a fixed plane. Line Z therefore, inthe drawing may be taken as a'base line and lines 111, D1, c1, and d1drawnrespectively through the shaft centers 14 in the respectivepositions A, B, C and D parallel with the line e1 which is the plan axisof shaft 11 will intersect line Z at the points 2111, zbl, 201, 2111 andzel respectively. Line ZM, parallel with line Z, indicates the maximumpermissible axial displacement of cone 15 necessary to obtain therequired amount of lateral displacement of shaft 14 to attain itsmaximum distance from shaft 11. If lines a2, 212-, etc., be now drawnparallel to lines 11, b1, 01, etc., until they intersect line ZM atpoints za2, zb2, 202, 2112 and 2:22, lines connecting points zal-za2,zb1- -zb2, zc1zc2, zd1zd2, and ze1-ze2, each will indicate the requiredline of adjustment movement of the motor to give the required axialmovement of shaft 14, concurrent with the required lateral movement, toat all times maintain the medial transverse plane between the cone paircoincident with the medial transverse plane of pulley 10, and the beltwill at all times remain in a plane at right angles to the axes ofthetwo shafts 11 and 14.

In the diagram the assumption has been that the necessary lateralmovement of shaft 14 in position A will be approximately 2%"; in podtionB approximately 3"; in position C approximately 3%; in position Dapproximately 5%" and in position E approximately 8 /2, and thecorresponding angular positions of the guideway relative to the beltline Z will be respectively approximately 13 degrees, 11 degrees, 9 /2degrees, 6% degrees and 4 degrees.

I have not attempted to state, to a high degree of accuracy, the preciseguide angles because slight variations from mathematical accuracy arepermissible without serious deterioration of the belt, but, by followingthe graphic method outlined above, the necessary guide angle may beapproximated within reasonable commercial limits, said guide angle beingin all instances materially less than the pitch of the cone, and beingdependent upon the relation between the adjustment plane of theadjustable shaft and a parallel plane which passes through the axis ofthe fixed shaft.

Theoretically, variations in the minimum distance' between the shaftcenters introduces another variable because variations in belt lengthwill be accompanied by variations in the percentage of arc contactbetween the belt and cones but in power transmission units for whichthis construction is especially designed most economically are soproportioned that the minimum distance between the shafts varies only acomparatively few inches and the belt length variable has been found tobe so inconsequential that it may be safely ignored. In any event, thegraphic method of determining the adjustment angle takes care of thisvariable.

I have found in actual practice that when the guide angle is properlyproportioned, in accordance with the above disclosure, my improvedspeed-varying transmission unit may be readily adjusted through itsentire range without causing any tendency in the.belt to ride theflanges of the fixed diameter pulley or to twist between the cones, andthat the unit is exceedingly efficient in small units where the twoshafts 11 and purposes, this angular relation may be determined in thefollowing manner:-

Where B=Belt length.

carriage 30, serves to shift carriage 30 in guide 31 to adjust theapparatus for desired speed. a

It willbe readily understood thatthe cone pair Let V=eifective diameterof sheave 10.

X=maximum effective diameter of discs 15 and 15'. N=Minimum effectivediameter of discs 15 may be m e upon h driven Shaft and the andcooperating grooved belt pulley may be mounted CX=Mmimum distancebetween the Shafts upon the motor or driving shaft, without departl1 and14 ing, from the spirit of my invention. Cs=Maximum distance between theshafts I 01mm as my mYentlon:

11 and iiig tifiiii fifitii iiii i ffiv s12; compns a a 1 s Angl1ebetweenlam of haft 54 and the on the motor shaft, an oppositely setfriction cone p ane Home to axes of Shafts 11 an axially shiftablerelative to the first cone, 9. spring I carried by the shaft and actingupon said second cone to yieldingly urge it toward the first cone, Q fltan a V-belt' coacting .with said two cones, a fixeddiameter pulleycoacting with and laterally Then confining. said V-belt, anangularly setsup- X tan A I tax. 5: T V X-'V N+V H tan S= I D X- N) I V 2 a i l flal)t N z 2 c,

This expression may be condensed to read t gujdeway f r said mdtor, theam tgn A of said guideway being angularly related to the tan S=-' axisof the. cones according to the following z y formula: While, as has beensaid, the above calculations will give results which arefairlysatisfactory, the following formula is an exact expression of thea value of the required angle between the axis of I 2. A speed-varyingpower-transmission unit the screw shaft 54 and the plane normal to thecomprising a base, a guide-way angularly adjustaxes of the shafts 11 and14. able on the base, a carriage slidably mounted in pendicular distancefrom shaft 11 on the carriage, a cone-pair carried by the shaft to theplane generated by movement of said motor and one cone spring biasedaxially tan S- of shaft 14. toward the companion cone, means by whichthe This ex ression ma be Sim 'nfied to read carriage may be positionedalong the guideway,

p y 1 p and a r-belt to cooperate with the cone pair.

tan fl 3. A speed-varying power transmission mech-- T anism comprising adriving shaft and a driven Where T equals the difference between theShaft, a friction c0116 axially fixed On 0 6 0! projection of 3,, on ttravel plane of the axis said shafts, an, oppositely set frictionconeaxially of shaft 14 and the projection Of'Cx on said travelShiftable relative to the first n and p i ed p1ane l v upon saidlast-mentioned shaft, a spring carried It will be understood, of course,that the pulley y said last-mentioned shaft and acting up 10 and theentire machine to which itis atsaid second cone t y ldin ly urge it t wad th tached, might be the laterally and axially shiftfirst C0118, fi d-da fl p y mounted p able element but as a general proposition that willthe other Shaft, a v-belt COflOting With Sa d two be an inconvenientarrangement. cones and said pulley and laterally confined In order toadapt the power unit for. ready e y, 9- PD for One Of Said ShaftsShiftapplication to various machines without the ab nsver y he s 0! SShaft, an necessity of placing the driving shaft in any pargularly setay f said pp Said ticular adjustment plane relative to the drivenguideway bei g a ly related to the axis of shaft, the motor 13 iscarried on a stud 50 jourthe cones-acco din o t e followin ul naled incarriage 30 and held in adjusted position by a set screw 51. Guide 31is, in turn, rotatably' adjustable on base 52 and held in adjustedposition by set screw 53. Bythis arrangement guide I 4. Apower-transmission unit' comprising a 31 may be set at a properanglerelative to the base, a guideway angular-1yadjustablev on the axis ofthe driven shaft 11 and the'driving shaft base, a carriage s dably munted in said d 14 may be brought to parallelism with shaft 11 way, amotor angularly adjustable on the carfor any angular position of guide31. A screw riage about an axis transverse to the plane of 54, journaledin guide 31 and threaded through the g'uideway, a belt-receivingstructure carried by the motor shaft and formed to laterally restrain aV-belt, and means by which the carriage may be adiustably positionedalong the guideway.

5. A speed-varying power-transmission unit comprising a shaft, asecondshaft, a pair of oppositely set friction cones mounted on one ofsaid shafts, one of said cones being axially shiftable, a spring urgingsaid one cone toward the other cone, 2. fixed-diameter pulley mounted onthe other of said shafts, an edge-active belt coacting with said conesand with said pulley andlaterally confined by said pulley, a supportingguideway for one of said shafts, the axis of said guideway beingangularly related to the axes of said shafts according to the followingformula:

other cone, a fixed-diameter pulley mounted on I the other of saidshafts, an edge-active belt coacting with said cones and with saidpulley and laterally confined by said pulley, a supporting guideway forone of said shafts, the axis of said guideway being angularly related tothe axes of said shafts according to the following formula:-

8."A speed-varying power-transmission mechanism comprising a drivingshaft and a driven shaft, a frictioncone axially fixed on one of saidshafts, an oppositely set friction cone axially shiftable relative tothe first cone and splined upon said last-mentioned shaft, means actingupon said second cone to yieldingly urge it toward the first cone, afixed-diameter pulley mounted upon the other shaft, a V-belt coactingwith said two cones and said pulley and laterally confined thereby, asupport for one of said shafts shiftable transversely of the axis ofsaid shaft, an angularly set guideway for said support, said guidewaybeing angularly related to the-axis of the cones according to thefollowing formula:

PAUL B. REEVES.

- tan S=

